[PATCH] Convert a vselect into a concat_vector if possible

[Elena Demikhovsky]

================
Comment at: lib/Target/X86/X86ISelLowering.cpp:17876
@@ -17840,1 +17875,3 @@
 
+  if (LHS.getOpcode() == ISD::CONCAT_VECTORS &&
+      RHS.getOpcode() == ISD::CONCAT_VECTORS &&
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You do not check that the types are legal. On what stage this optimization should happen? <2 x float> that you take in your test is illegal.

http://reviews.llvm.org/D3916